Crystal oven



March 23, 1948. A. E. MILLER 2,438,345

CRYS TAL OVEN Filed Dec. 5, 1946 JNVENTOR. \54 aNnL LIGHT AU6U57.'MILLER @gba/Mh 5 A H TTORNE YS Patented Mar. 23, 1948 UNITED STATESPATENT OFFICE CRYSTAL OVEN August E. Miller, Cliffside Park, N. J.Application December 5, 1946, Serial No. 714,275

9 Claims. 1

The invention relates to a piezo crystal oven and holder. It isdesirable if not essential that the crystal used in oscillating circuitsbe stabilized with respect to its oscillating frequency. One of thefactors which affect the frequency of oscillation of a crystal is thetemperature at which it operates. For this reason it is customary toprovide means for maintaining the crystal at a predetermined operatingtemperature so that there will be no variation in frequency responsebecause of temperature changes.

Crystal controlled oscillator circuits constitute a part of the radioand radar equipment on aircraft which are subject to wide variations intemperature. It is also important that crystal ovens for aircraftservice occupy a minimum of space. This requires an efficientutilization of the space required for the crystal oven.

It is an object of the invention to construct a crystal oven whichelectively maintains the temperature of the crystal at the desiredoperating temperature and a crystal holder which utilizes spaceefficiently so that the oven has minimum dimensions.

Another object is to construct a crystal oven and holder in which a fastheater with a control thermostat is utilized to quickly raise thetemperature of the oven to approximately the desired operatingtemperature, and a slow and more accurate heater and control thermostatfor accurately maintaining the operating temperature of the crystalwithin the oven.

Another object is t construct a crystal oven and holder which can beeasily assembled and disassembled for repair or replacement of parts.

Other objects of the invention will be more apparent from the followingdescription when taken in connection with the accompanying drawing,which illustrates a preferred embodiment thereof, in which:

Figure 1 is a cross-sectional view through the oven.

Figure 2 is a top view 0f the crystal holder.

Figure 3 is a cross-section through the holder taken on line 3-3 ofFigure 2.

Figure 4 is a circuit diagram of the electrical connections of theheaters and their thermostats and of the crystals.

The crystal oven includes a casing which may be constructed in anysuitable fashion, that illustrated being made up of several parts,including a side wall lll, a top cover i i, and a base I2, which partsmay be of heat insulating material such as Bakelitel The case may befurther heat insulated by a metal lm 3 uponthe sides and top which maybe secured thereto and pads i4 such as of glass wool. The base carries aconnecting base l5 having a series of contact prongs IS which areelectrically connected with the various elements of the oven.

Within the case is a crystal holder I9, shown in cylindrical form withflat top and bottom faces, having at least one and preferably twocrystal cavities 2U. The pair of crystal cavities are spaced upon eachside of the center of the holder and spaced from each other. Thesecrystal caviF ties preferably extend completely through the crystalholder between the flat faces thereof. rEhe crystal holder is of metal,and preferably a light weight metal such as aluminum, because of thegood heat conducting properties of metal which readily transmits heattherefrom to the crystal structure.

A slow heater thermostat cavity 2l extends diagonally from the bottomedge of the holder to the opposite top edge between the crystalcavities. A fast heater thermostat cavity 22 also ei:- tends into thecrystal holder from one edge thereof and between the crystal cavitiesand intersects the slow heater thermostat cavity 2l. The fast heaterthermostat cavity is adjacent to the top face of the holder. A slowheater thermostat is mounted in the diagonal cavity and a fast heaterthermostat 24 is mounted in its cavity iii.

A pair of spaced holes 21 extend between the faces of the crystal holderI9 and in the top face of the holder is a groove 28 extending at leastbetween the holes. The holes are adjacent the end of the crystalcavities. A fast heater 29, which is preferably U-shaped in form, hasits legs extending through the holes and its connecting portion lieswithin the groove 28. An electrically insulating glass fabric 30 extendsaround the crystal holder and a slow heater 3l is wound around theholder and fabric. This heater winding prefer ably is non-inductive withparallel wires and the screws 32 are the terminals therefor. A screw 33holds the looped end of the slow heater. Adjustment of the position ofthe insulators 31 upc-n the looped end of the slow heater adjusts theposiw tion of the crossed or shorted ends and thereby enables the lengthand hence the resistance of this heater to be accurately adjusted. It isconnected in series with the slow heater thermostat 23 and the U-shapedheater is'connected in series with the fast heater thermostat 24. Thetwo heaters and particularly the fast heater brings the temperature ofthe holder and crystal assembly rapidly to the desired operatingtemperature of about degrees whereupon the slow heater accuratelymaintains the parts at this temperature with the aid of the metalliccrystal holder which serves as a heat reservoir or stabilizer. Suitablewires W connect the heaters in series with their respective thermostatsand with the contact pins or prongs I6.

A crystal assembly 34 is mounted in each crystal cavity 20, whichassembly may be of any suitable kind. Such assemblies generally includea crystal, an electrode mounted upon each side thereof, and a caseretains the electrodes and crystal in assembled relation. The crystalholder has a top plate 35 secured to the top flat face of the holder inorder to enclose the cavities therein. A bottom plate 36 is secured tothe bottom iiat surface of the holder to enclose this end thereof.Suitable holes are provided through the bottom plate for connectingwires to the electrodes of the crystal assemblies and to make connectionwith the fast heater.

Aheat insulating baffle plate 39 is secured to the bottom plate 36 suchas .by screws 33 and is spaced therefrom by spacing washers 4Q. rihebaffle plate also is provided with holes for the passage of wires to thecrystal electrodesvand to the heaters or their thermostats. The bailleplate is in turn secured to the base l2 such as by screws #213 so thatthe entire crystal holder assembly is secured thereto. The baille plateis spaced from the base I2 by spacing washers 4I.

Suitable wires W extend from the prongs it to the crystal electrodes andto the thermostats and heaters as well as between the heaters andthermostatsso that the entire crystal oven may be plugged into a,socketV and thereby establish electrical connection between the variousparts thereof and the circuit of which it will form a part.

The crystal oven provides a compact arrange-n ment of the parts thereofas well as a pair. of heaters for rapidly raising the temperature to thedesired operating temperature and then accurately maintaining the same fThis invention is presented to iill a need for 'improvements in crystaloven. It is understood that various modifications in structure, as wellas changes in mode of operation, assembly, and manner of use, may andoften do occur to those skilled in the art, especially after benefitingfrom the teachings of an invention. Hence, it willl be understood thatthis disclosureis illustrative of performed means oi embodying theinvention in useful form by explainingV the construction, operation Vandadvantages thereof.

What is claimed is:

l. A piezo electric crystal holder comprising a metallic housing of suchdimensions as to enclose heater and control elements and at least onepiezo crystal assembly, at least one crystal cavity therein to receive acrystal assembly including; the piezo crystal, crystal electrodes andcase, a slow electric heater coil wound around the metallic housing,spaced holes through the housing, a fast electric heater lextending intothe spaced holes, a pair of thermostat cavities in the housing, and athermostat in each cavity, one thermostat being connected with eachheater to control the current supplied to its respective heater. f

2-. A piezo electric crystal holder comprising a metallic housing ofsuch` dimensions as to enclose heater and control elements and at leastone piezo crystal assembly, at least one crystal cavity therein toreceive a crystal assembly including the piezovcrystal, crystalelectrodes and case, a

slow electric heater coil wound around the metallic housing, a pair ofspaced holes through the housing, a groove in one face of the housingextending between the holes, a U-shaped fast electric heater having itsarms extending into the spaced holes and the connecting portion receivedwithin the groove, a pair of thermostat cavities in the housing, and athermostat in each cavity, one thermostat being connectedwith eachheater to control the current supplied to its respective heater.

3. A piezo electric crystal holder comprising a cylindrical metallichousing of such dimensions as to enclose heater and control elements anda pair of piezo crystal assemblies, a pair of crystal cavities thereinspaced from the center of the housing, each cavity receiving a crystalassembly including the piezo crystal, crystal electrodes and case, aslow electric heater coil wound around the cylindrical surface of themetallic housing, a pair of spaced holes through the housing andparallel with the crystal cavities and adjacent thereto, a groove in oneface of the housing extending between the holes, a U-shaped fastelectric heater having its arms extending into the spaced holes and theconnecting portion received within the groove, a pair of thermostatcavities in the housing between the crystal cavities, and a thermostatin each cavity, one thermostat being connected with each heater tocontrol the current supplied to its respective heater.

e. A piezo electric crystal holder comprising a cylindrical metallichousing of such dimensions as to enclose heater control elements and apair of piezo crystal assemblies, a pair of crystal cavities thereinspaced from the center of the housing, each cavity receiving a crystalassembly including the piezo crystal, crystal electrodes and case, aslow electric heater wound around the cylindrical surface of themetallic housing, a pair of spaced holes through the housing andparallel with and adjacent to the crystal cavities, a groove in one faceof the housing extending between the holes, a U-shaped fast electricheater having its arms extending into the spaced holes and theconnecting portion received within the groove, a thermostat cavity inthe housing extending from one edge of the metallic housing diagonallyto the other edge and between the crystal cavities, a second thermostatcavity extending from the circumference of the metallic housing to thefirst thermostat cavity and located adjacent to a face ofthe metallichousing, and a thermostat in each cavity, each thermostat beingconnected with its respective heater to control the current suppliedthereto.

5. A piezo electric crystal oven comprising a metallic housing havingflat top and bottom faces and of such dimensions as to enclose heaterand control elements and at least one piezo crystal assembly; at leastone crystal cavity therein to receive a crystal assembly including thepiezo crystal, crystal electrodes and case; a slow electric heater coilwound around the metallic housing, spaced holes through the housing, afast electric heater extending into the spaced holes, a pair ofthermostat cavities in the housing, a thermostat in each cavity, onethermostat being connected with each heater to control the currentsupplied to its respective heater, a top and bottom metallic coversecured to each face of the housing, an insulating baliie plate spacedfrom the bottom cover, an insulated case surrounding the housingincluding a base having electrical connecting prongs, and wiresconnecting the prongs with the heaters and the crystal electrodes.

6. A piezo electric crystal oven comprising a metallic housing havingflat top and bottom faces and of such dimension as to enclose heater andcontrol elements and at least one piezo crystal assembly; at least onecrystal cavity therein to receive a crystal assembly including the piezocrystal, crystal electrodes and case; a slow electric heater coil woundaround the metallic housing, a pair of spaced holes through the housing,a groove in one face of the housing extending between the holes, a,U-shaped fast electric heater having its arms extending into the spacedholes and the connecting portion received within the groove, a pair ofthermostat cavities in the housing, a thermostat in each cavity, onethermostat being connected with each heater to control the currentsupplied to its respective heater, a top and bottom metallic coversecured to each face of the housing, an insulating baille plate spacedfrom the bottom cover, an insulated case surrounding the housingincluding a base having electrical connecting prongs, and wiresconnecting the prongs with the heaters and the crystal electrodes.

7. A piezo electric crystal oven comprising a cylindrical metallichousing having flat top and bottom faces and of such dimensions as toenclose heater and control elements and a pair of piezo crystalassemblies, a pair of crystal cavities therein spaced from the center ofthe housing; each cavity receiving a crystal assembly including thepiezo crystal, crystal electrodes and case; a slow electric heater coilwound around the cylindrical surface of the metallic housing, a pair ofspaced holes through the housing and parallel with the crystal cavitiesand adjacent thereto, a groove in one face of the housing eX- tendingbetween the holes, a U-shaped fast electric heater having its armsextending into the spaced holes and the connecting portion receivedwithin the groove, a pair of thermostat cavities in the housing betweenthe crystal cavities, a thermostat in each cavity, one thermostat beingconnected with each heater to control the current supplied to itsrespective heater, a top and bottom metallic cover secured to each faceof the housing, an insulating baiile plate spaced from the bottom cover,an insulated case surrounding the housing including a base havingelectrical connecting prongs, and wires connecting the prongs with theheaters and the crystal electrodes.

8. A piezo electric crystal oven comprising a cylindrical metallichousing having flat top and bottom faces and of such dimension as toenclose heater control elements and a pair of piezo crystal assemblies,a pair of crystal cavities therein spaced from the center of thehousing; each cavity receiving a crystal assembly including the piezocrystal, crystal electrodes and case; a slow electric heater woundaround the cylindrical surface of the metallic housing, a pair of spacedholes through the housing and parallel with and adjacent to the crystalcavities, a groove in one face of the housing extending between theholes,

a U-shaped fast electric heater having its arms extending into thespaced holes and the connecting portion received within the groove, athermostat cavity in the housing extending from one edge of the metallichousing diagonally to the other edge and between the crystal cavities, asecond thermostat cavity extending from the circumference'of themetallic housing to the rst thermostat cavity and located adjacent to aface of the metallic housing, a thermostat in each cavity, eachthermostat being connected with its respective heater to control thecurrent supplied thereto, a top and bottom metallic cover secured toeach face of the housing, an insulating baille plate spaced from thebottom cover, an insulated case surrounding the housing including a basehaving electrical connecting prongs, and wires connecting the prongswith the heaters and the crystal electrodes.

9. A piezo electric crystal oven comprising a cylindrical metallichousing of such dimensions as to enclose heater control elements and apair of piezo crystal assemblies, a pair of crystal cavities thereinspaced from the center of the housing, each cavity receiving a crystalassembly including the piezo crystal, crystal electrodes and case, aslow electric heater wound around the cylindrical surface of themetallic housing, a pair of spaced holes through the housing andparallel with and adjacent to the crystal cavities, a groove in one faceof the housing extending between the holes, a U-shaped fast electricheater having its arms extending into the spaced holes and theconnecting portion received within the groove, a thermostat cavity inthe housing extending from one edge of the metallic housing diagonallyto the other edge and between the crystal cavities, a second thermostatcavity extending from the circumference of the metallic housing to therst thermostat cavity and located adjacent to a face of the metallichousing, and a thermostat in each cavity, each thermostat beingconnected in series with its respective heater to control the currentsupplied thereto, a top and bottom metallic cover secured to each faceof the housing, an insulating baille plate spaced from the bottom cover,an insulated case surrounding the housing including a base havingelectrical connecting prongs, and wires connecting the prongs with theheaters and the crystal assemblies.

AUGUST E. MlLLER.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 1,044,269 Shaler Nov. 12, 19121,831,151 Walker Nov, 10, 1931 1,955,359 Crossley Apr. 17, 19341,995,355 Koerner Mar. 26, 1935 1,996,569 Byrnes et al. Apr. 2, 19352,102,783 Bokovoy Dec. 21, 1937 2,276,930 Clark Mar. 17, 1942

